Water introduced into fiber optic cables can deteriorate the transmission capabilities of optical fibers. To prevent such degradation, water-blocking has historically been accomplished in fiber optic cables by using gels and/or greases. Water blocking, petroleum-based filling gel used in optical fiber cables blocks the ingress of water into the cable by filling the free space inside a buffer tube and mechanically couples the optical fibers to the buffer tube. That notwithstanding, such thixotropic gels and greases are messy (i.e., during splicing operations) and are therefore disfavored.
Dry, water-blocked fiber optic cables eliminate the cleaning problems associated with these gels. To create a dry cable, the filling gel may be replaced by a water-swellable element (e.g., a tape or yarn carrying or impregnated with a water-swellable material). Typical water-swellable elements include water-swellable particulate powders. Such powders are typically composed of superabsorbent polymers that, when bound on or impregnated in a tape or yarn, are dry to the touch and, accordingly, are readily removed from cables during splicing operations.
Despite the benefits of a dry powder system, the particulate powders now employed present other problems. Manufacturers have reduced the size of cabling to reduce bulk and thereby permit easier installation. This size reduction, however, increases the likelihood that the optical fibers within the fiber optic cable will be subjected to mechanical loads. To the extent particulate powders are employed, such mechanical loads can cause point-contact stresses between the discrete particles and the optical fibers. This can result in undesirable microbending and other optical attenuation.
Thus, there is the need for a dry water-blocking system that reduces the potential for microbending.